At the postmatch press conference Kei told the Japanese media that he couldn't move at all during a warm-up in the morning and even trying to stretch to serve was painful. He was aware that he had probably had no chance to win today but decided to give it a go.
But he thinks the injury is not serious and he would probably need just a week's rest.

Hope he's right and won't make the same mistake as last year, playing when he really shouldn't be!